1. Field of the Invention
This invention relates to a structure for a running system in a vehicle, with provisions for right and left running wheels, hydraulic cylinders extensible and retractable in opposition to each other in response to the axle-tilting displacement of the wheels as the wheels rise and lower in turn in opposition to each other, a conduit connecting the cylinders to each other with an on-off valve interposed therebetween to be arbitrarily manueverable thus allowing the lock up of both cylinders, and a supply conduit for supplying oil thereto.
2. Description of the Prior Art
Work vehicles equipped with the structure mentioned hereinabove are advantageously adapted to travel even on irregular terrain, while keeping their body stable by avoiding any substantial rolling of the body by effectively absorbing in the axle-suspension means any possible axle-tilting irregular displacement of the wheels as they are raised and lowered in opposition to each other, and on the other hand also to perform the intended work with the vehicle stationed firmly with the body in a stable position by avoiding any substantial rocking movement under reaction of the work force, by locking up both cylinders, and thus having all the wheels stand securely on the ground.
However, when performing for instance lateral excavation work with both cylinders locked up as mentioned above, the vehicle body might be subjected to an alternating movement of the body due to the reaction force resulting from such work. Furthermore, when such reaction force is relatively large and acts very abruptly the hydraulic cylinder on one side of the vehicle is subjected to a high compressive stress which raises the inner pressure therein and which has conventionally resulted in oil leakages from the cylinder and from the conduit connecting the cylinder to the on-off valve. Meanwhile, the second hydraulic cylinder on the other side is subjected to a high tensile stress which rapidly lowers the pressure within the cylinder, thus resulting in the bubbling of the gases within the oil of the second cylinder (as may occur upon sudden decompression of gases disolved in a liquid under big pressure and also upon intrusion of external gases) and in the conduit connecting the second cylinder to the on-off valve. Since the rolling movement of the vehicle body is attenuated normally rather gradually in the course of the repeated transverse rocking cycles, the big reaction force creates repeatedly the above described effects on both cylinders, causing gradual loss of the oil in the cylinders, and making it impossible after awhile to firmly maintain the working position of the vehicle as it was originally set up.